The invention relates generally to a jig for the treatment of a textile web and more particularly to a method of treating a web of material in a jig with improved uniformity of application.
A jig having a housing with first and second housing portions, the first housing portion containing two mutually parallel winding rollers, a web of material to be treated mounted on the rollers, means defining a path along which the web can be reversibly wound back and forth onto the rollers, and with the second housing portion containing a liquid bath reserve is described in DE-OS 34 21 152. The disclosed jig also includes an applicator system uniformly applying a proportioned quantity of treatment liquor to the web as the web passes along a portion of the path disposed between the winding rollers above the level of the bath reserve in the second housing portion.
As further disclosed in DE-OS 34 21 152, the web of material in the jig housing runs along a path formed between two deflection rollers disposed below the winding rollers, which are approximately horizontally positioned in spaced relation above the level of the bath reserve in the jig housing. Between the deflection rollers a slitted discharge tube extending above and across the width of the web is arranged from which treatment liquor is discharged onto the web as it slides past the discharge slit. The treatment liquor is supplied from the bath reserve contained in the lower part of the jig housing. The liquor, in part, drips back from the web into the bath reserve, and in this manner is continuously circulated within the jig in a predetermined proportion.
One of the problems with jigs of this type is that the beginning of the web is treated with a bath having a higher concentration than and different consistency from the bath present at the end of the web. Treatment liquor that had been in contact with the web via the discharge slit drips into the lower portion of the jig in the aforementioned manner. However, since some of the treatment agents such as dyes, acids, salts, oxidants, soaps, fastness improvers, etc., have been absorbed by the web, liquor dripping from the web is in a diluted condition and thereby changes the overall consistency of the liquid in the bath reserve. Since this liquid is ultimately applied to the web at the end of the web treatment process, the result is nonuniform application of the treatment liquor.
Another problem encountered in conventional jigs is the alteration of the bath consistency which occurs during passage of the web through the bath reserve contained in the vat-like lower portion of the jib. This produces nonuniform liquor application not only due to the alteration of the bath consistency, but also due to the attendant accidental changes in the absorption capacity of the web over its surface area.
Previous solutions to these problems have been unsatisfactory. One such solution is known from FR-PS 1,037,560 which discloses continuously pumping off the liquid contained in the vat-like lower portion and reapportioning the liquid reintroduced into the jib. This solution involves considerable cost and does not solve the problem of nonuniform distribution of the reproportioned liquid caused by passage of the web through the bath reserve.
A prior solution to the problem of variation in bath supply consistency during a single web pass, i.e., when the entire web length completely passes from one winding roller to the other, in earlier jig systems was to approximately even out the conditions in the web by repeatedly winding the web back and forth between the winding rollers.
This solution greatly multiplies the cost of treatment because of the large number of successively performed processes carried out in the jig that must be repeated. For example, the succession of treatment steps may be desizing--rinsing boiling off--rinsing; bleaching--rinsing; and dye application with the addition of additives and/or developers, etc. These discrete processes are all divided into several passes, and in all of them repeated draining of the treatment baths and respective reheating is necessary. Treatment times of 4 to 6 hours are not unusual.
Another problem with prior jigs is maintenance of the important ratio of bath to web area when the jig is subject to different loads. For the jig to function properly, a certain minimum content of bath is needed. The bath supply must be matched with different total surface areas of the webs treated in the jig, i.e., the same amount of bath is used to treat, on the one hand, wide as well as narrow webs of equal length and, on the other hand, shorter and longer webs. This makes it difficult to keep the treatment result uniform and requires checking by expensive interim sampling.
All of the above-noted problems result in undesirable nonuniform treatment of the web.